In recent years, with the rapid expansion of visual communications, the use of slide transparencies has become increasingly popular. One of the most convenient techniques for visual presentation involves the use of 35 mm slide projectors which project slide transparencies on a screen for easy audience viewing. Such techniques are widely used in educational courses, and frequently during business, professional and governmental seminars. For maximum utilization of such slide transparencies, a simple and convenient procedure is needed for duplicating documents and other objects as projectable images on slide transparencies.
While silver halide and diazo film have been used in making such transparencies, the imaging and developing process for such films require the use of a darkroom or special equipment and, for best results, require trained operators. In contrast, electrophotography will produce excellent high-resolution images in a convenient and economical manner. At the present time, electrophotographic cameras are of limited availability and relatively expensive in price and not entirely satisfactory in performance. The only commercially available electrophotographic slide-processing system for making slide transparencies involves the use of fully mounted slide frames. Such frames consist of a film laminated between two rectangularly apertured frames. The plane of the film is recessed inwardly from the outer surface because of the thickness of the frames. In effect, the outer surface of the frame provides the processing surface plane of the camera. One such system is disclosed in the Yamaji patent, U.S. Pat. No. 3,694,069. In the use of these slides, imaging irregularities are sometimes encountered, particularly at the peripheral edges of the film adjacent the frame edge. This irregularity appears to be caused by the surface tension of the liquid toner which has a tendency to bridge over and not fully wet out the areas of the film adjacent the frame.
In the Yamaji camera, the fully mounted frame is provided with a hole to enable contact with the photoconductive layer of the film, and the frame moves through the apparatus in one direction. As a result, a relatively large processing block is required to provide a path or track of sufficient length for unidirectional movement of the film during processing. At various locations along the unidirectional processing path, the film is first charged by a corona charging unit, moved to an imaging location and, after imaging, advanced to still another site for developing. The development is carried out by the use of a rotatable, absorbent roll, which picks up toner from a bath and applies it to the film. Finally, the film is carried past fixing and drying stations.
The principal object of this invention is to provide an improved apparatus for automatically producing electrophotographic slide transparencies which apparatus is of compact size and economical to manufacture. The pre and post exposure processing of the film takes place on inverse, inextensive paths.
A further significant object of this invention is to provide an apparatus of above type wherein the film is automatically processed along a reciprocal path about half the length of the processing paths in commercially available electrophotographic cameras.
Another object of this invention is to provide an apparatus of the above type wherein the film being processed is disposed on one side of an open, foldable planar slide frame.
It is a further object of this invention to provide an apparatus of the above type wherein the open slide frame on which the film is carried is inserted and withdrawn along inverse processing paths by reversal of the same drive means and by automatic, sequential operation of the imaging and developing elements.
Yet another object of this invention is to provide an apparatus wherein positive air pressure is provided along a portion of the processing path during withdrawal of the imaged film.